The present invention relates to hammer drills used for, for example, boring concrete.
A hammer drill is a tool that applies a percussive impact to a drill bit in the axial direction while rotating the drill bit about its axis. The motion of a reciprocating piston propagates to a hammer, which is supported through an air spring, as the mechanism by which to provide the percussive impact. However, it is difficult to adjust the percussive force in hammer drills using this type of mechanism for providing the percussive impact, resulting in bent or broken drill bits when small drill bits are used. Conversely, when drill bits with larger diameters are used, with hammer drills with relatively small percussive forces, it is difficult to maintain the speed of the boring operations, causing the boring operations to be too time-consuming.